DatabaseContentProvider test

Adding tests for the DatabaseContentProvider. Now the test is checking if the inserted data using the content provider is correct
in the database. #2
Imports organization

The Android Studio orginazed the imports
Moving utility test classes

Moving HttpStackMock and Util class to other package
Fix table creation problem

Some tables were being created with the wrong type.#3
Not hide insert problems

Changed the insert method in the DatabaseContentProvider to throw exception if some problem occurs.

Issue #2